They know him best, having employed the outside linebacker under top football executive John Spanos all five seasons since A.J. Smith drafted him 18th overall in 2012.

While doubling down on Ingram would be a sensible move on a few counts, the market-place could price him out of the team’s plans.

A franchise tag on Ingram will cost the Chargers about $15.3 million this season.

The deadline to apply the tag to a potential free agent is March 1. With or without a tag, the Chargers and Ingram’s agent could still work out a multi-year contract.

The logic to “tag” Ingram is two-fold: 1) Ingram is a good all-around performer and the best outside linebacker on the roster; 2) a short contract reduces the risk on a player who will turn 28 in April and missed most of his second and third seasons due to injury.

A pairing of Joey Bosa and Ingram would give the Chargers two above-average pass rushers to go with Pro Bowl-caliber cornerbacks Casey Hayward and Jason Verrett.

In my view Ingram is coming off his best all-around season, although he had more sacks (10.5) and tackles (52) in 2015.

In comparison to the Chargers, both the Bucs and Titans have far more cap space.

Tennessee, though, still owes sizable salaries to veteran outside linebackers Derrick Morgan, 28, and Brian Orakpo, who will be 31 in July.

Former Chargers special teams coach Craig Aukerman joined Tennessee’s staff this offseason as assistant special teams coach.

Ingram’s size and versatility are a fit for Titans coordinator Dick LeBeau’s design, although a stickler like LeBeau could be turned off by Ingram’s lapses in containment against the belly option.

The Colts, who are deep in cap space and appear to be in “win now” mode, have need for a disruptive edge player such as Ingram.

Ingram is younger than several Colts edge men.

Colts coach Chuck Pagano, brother of former Chargers coordinator John Pagano, will have the inside dope on him (John Pagano’s current employer, the Raiders, isn’t a good fit due to the presence of Khalil Mack, Bruce Irvin and Aldon Smith.)

With Bosa in particular, Ingram developed chemistry on stunts; however, new Chargers defensive coordinator Gus Bradley represents a change in scheme design, from base “3-4” to base “4-3,” although not a major one.

If Ingram leaves the Chargers, his replacement would be mysterious Jerry Attaochu, barring a surprise splash in free agency.

Three years after the Chargers invested two draft picks in him, Attaochu’s NFL aptitude is still largely an unknown due to an array of leg injuries that have limited the Georgia Tech all-time sack leader to less than 17 percent of the defense’s snap counts in his first and third seasons.

Attaochu has rare explosiveness and is only 24 years old going into his fourth season, but even with the six sacks he compiled over 15 games in 2015, due to the detours, his “peak” outing to date may have been his NFL debut in the 2014 opener at Arizona.

Preferring Attaochu over Ingram would free up a lot of salary-cap space.

The Chargers’ betting on Attaochu would represent as well a show of faith in the overhaul of the training and fitness staffs.

The 2016 starter opposite Ingram was Kyle Emanuel, who is adequate or better at setting the edge and also an emergency option at inside linebacker.

Emanuel, who will be 26 in August, is capable of leveraging blockers on pass rushes. Minus Ingram, the Chargers would be more apt to add outside linebackers who project as good pass rushers.